1. Field of the Invention
The present invention relates to an ink jet recording head which performs recording of an image onto a recording medium by discharging ink through a discharging opening, particularly to an ink jet recording head equipped with a discharging opening forming member having said discharging opening formed thereon.
Also, the present invention relates to an ink jet recording device provided with the ink jet recording head equipped with said discharging opening forming member.
2. Related Background Art
FIG. 1 is a perspective view schematically showing the external constitution of an ink jet recording device. In FIG. 1, 1 is an ink jet recording head which records a desired image by discharging ink based on a given recording signal (hereinafter called a recording head), 2 is a carriage which scans and moves in the recording line direction indicated by double-headed arrow B (main scanning direction) with the above head 1 carried thereon. The above carriage 2 is slidably supported by the guide shafts 3. 4 and moves in a reciprocal fashion in the main scanning direction as associated with the timing belt 8. The above timing belt 8 engaged with pulleys 6, 7 is driven by the carriage motor 5 through the pulley 7.
The recording paper 9 is guided by the paper pan 10 and conveyed with a paper delivering roller (not shown) pressure contacted with the pinch roller. This conveying is done by the paper delivering motor 16 as the driving source. The recording paper 9 being conveyed has tension applied thereto by the discharging paper roller 13 and the spur 14 to be pressure contacted against the heater 11 by the paper pressing plate 12 formed of an elastic member, and hence conveyed while being closely contacted with the heater 11. The recording paper 9, having ink jetted from the head 1 attached thereto is warmed by the heater 11, and &he attached ink is fixed onto the recording paper 9 through evaporation of water.
Reference numeral 15 represents a unit called a restoration system, which maintains the discharging characteristic of the ink under normal conditions by removing any foreign matter or ink increased in viscosity attached on the discharging opening (not shown) of the recording head 1.
On the recording region side of the restoration system unit 15, there is provided a cleaning blade 17 for cleaning foreign matter or ink droplets attached on the discharging opening surface, which is in contact with the surface on which the discharging opening of the recording head 1 is formed.
The recording head 1 mounted on the ink jet recording device as described above includes a discharging opening forming member 26 having a plurality of fine ink discharging openings 27 formed as shown in FIG. 2 (hereinafter called an orifice plate) and a head main body 29 provided with ink channels 24 communicating with the above discharging openings 27. And, a part of the above ink channels 24 is provided with an ink discharging energy generating member (not shown) utilized for discharging ink through the discharging openings 27. For example, when a heat energy generating element which generates heat energy is used as the energy generating member, ink is discharged through the discharging openings by utilizing the abrupt pressure change created by &he bubbles formed by the heat energy.
In the prior art, for the orifice plate 26 constituting the above recording head 1, a flat plate having discharging openings formed at predetermined positions has been used. The orifice plate 26 and the head main body 29 have been secured and bonded by use of a method such as pressure application for example after coating the entire surface of the bonding surface 26a of the orifice plate 26 or the bonding surface 25 on the side of the head main body 29 with a bonding agent and then effecting registration between the two. The bonding surface between the orifice plate 26 and the head main body 29 has been made as a flat plane in order to improve adhesion between the two.
However, in the above recording head 1, since the bonding agent intervening between the orifice plate 26 and the head main body 29 shrinks when hardened, stress is generated between these. Also, because there is a difference in the thermal expansion coefficient among the orifice plate 26, the bonding agent and the head main body 29, for example, stress is generated between these in a recording head of the type which utilizes heat energy as the ink discharging energy.
For example, the thermal expansion coefficients and curing shrinkages of borosilicate glass 7740 mentioned below as the material constituting the head main body 29, nickel mentioned below as the material constituting the orifice plate 26 and the two-liquid type epoxy formulated bonding agent Three Bond 2001 (main agent)/2105F (curing agent) mentioned below as the bonding agent used for effecting bonding of the both are shown below in Table 1.
TABLE 1 ______________________________________ Thermal expansion coefficient (.times. 10.sup.-7 / Constituent material .degree.C.) Curing shrinkage (%) ______________________________________ Borosilicate glass 32.5 -- Nickel 76 -- Bonding agent 750 2-3 ______________________________________
As is apparent from Table 1, there is 2 to 3% of curing shrinkage of the bonding agent, and the thermal expansion coefficients&are greatly different within the range of one order.
Therefore, there is sufficiently a concern that the stress as described above may be generated.
When such stress occurs between the respective constituent materials, deformation or destruction of the recording head such as distortion, fracture, crack, peeling, etc. is liable to occur, whereby resistance to environment, long term reliability or durability of the recording will deteriorate. Also, in such a recording head, lowering in uniformity of ink droplets or precision of discharging direction, etc. may arise resulting in disturbance of recorded images.
On the other hand, as the constitution which prevents the bimetal effect caused by the stress at the bonding portion, there is one described in Japanese Patent Application No. 56-162079 (Japanese Laid-Open Patent Application No. 58-63473, Japanese Patent Publication No. 64-12234).
The above arrangement absorbs the bimetaI effect occurring between the substrate 71 and the mounting plate 72 with the layer of the above adhesive 73 by forming a groove 74 on the mounting plate 72 on which the substrate 71 mounting the heat-generating element 73 is mounted, as shown in FIG. 3, filling an adhesive 73 having rubbery elasticity during curing into the groove 74 and adhering the mounting plate 72 to the substrate 71.
Whereas, when prevention of generation of stress by filling an adhesive having rubbery elasticity into the groove is applied to the ink jet recording head, there is a specific concern that ink may seep out by application of stress on the above adhesive.
For solving this problem, when an adhesive having the characteristic of excellent ink resistance and which is increased in hardness by curing is filled in the groove, the stress absorbed by the rubbery elasticity of the adhesive becomes unabsorbed, whereby there is no resultant effect of buffering the stress.
Accordingly, one may consider choosing a bonding agent excellent in ink resistance and having rubbery elasticity or choosing materials in order to reduce the curing shrinkage of the bonding because of the difference in thermal expansion coefficient between the respective constituent materials. However, it is very difficult to find materials which satisfy all of the various conditions of workability, bondability, ink resistance, etc.